This invention relates to an improvement in tool joints by which tubular members, such as drill pipes used in drilling oil and gas wells, are disconnected with less torque and is directed to the application of disconnecting a plurality of lengths of drill pipe, such as three lengths of pipe, or a unit of three pipe lengths, also referred to as a "stand" or "triples," to improve "triple back reaming" where "triple back reaming" is the preferred method of withdrawing a string of drill pipe out of a well bore, whether offshore or onshore. Reaming is accomplished by the drill pipe as it is being rotated and withdrawn.
It is to be understood that this invention improves the method of breaking out a stand of drill pipe by reducing the torque at one selected joint, but it also will be apparent to those skilled in the art that this invention has other applications. To facilitate disclosure, however, this invention is being described in connection with, and as an improvement of, the method of triple back reaming as an example of one application of this invention.
Back reaming in triples is today a preferred method of withdrawing a string of drill pipe from a well bore in those systems where rotating power is applied from above the platform, such as in the rigs utilizing the power drilling unit (top drive unit) of the U. S. Pats. to Boyadjieff Nos. 4,421,179; 4,437,524; 4,449,596 and 4,458,768 or the side drive system of Krasnov as disclosed and claimed in the copending U.S. application for patent Ser. No. 762,507, filed Aug. 5, 1985 and entitled "Side Drive Drilling."
Thus, in back reaming in triples, the drive spindle, or drive stem, is connected to the top of the three lengths of drill pipe being held by the spider at platform level and then is gradually raised by the traveling block on the drilling unit as the drill pipe is rotated until the lower joint of the three drill pipe lengths is above the platform. Rotation of the drill pipe is in the same direction in reaming as in drilling. Then, drill pipe rotation is stopped and the top pipe length of the next drill pipe length of the string is held by the spiders. Next, the break-out tongs and backup tongs break-out the lower joint of the stand of pipe. Later, a power tong on the drill unit is also used to disconnect the drive spindle from the top drill pipe length. Thereafter, the stand of pipe is then moved to one side of the drilling axis by the rig elevator. This procedure is repeated until the entire drill pipe string is withdrawn to the rig. This method of triple back reaming is disclosed in the U.S. Pat. No. 4,449,596, supra.
Because of the torque required to break-out the top joint from the drive spindle, the power tong has to be made part of the drilling unit. Additionally, when a break-out torque is applied to the lower point of the stand, break-out on one of the other three joints may occur first--an obviously undesirable result.
This invention reduces the torque required to break-out the top joint of the stand, thus insuring that the stand will be disconnected at this joint. This invention also eliminates the need for a power tong in the drilling unit.